The present invention relates to the making of bevel gears.
Bevel gears are made, for example, by placing a cylindrical, metallic (e.g., steel) blank into a die having a cavity portion contoured in accordance with the "negative" of the gear to be made; further, a punch is used, coaxially received by a control sleeve or counterpunch, to force the blank into the die cavity for press-forming the gear. This kind of method is disclosed, for example, in German Pat. No. 24,46,413; see also U.S. Pat. Nos. 3,731,516 and 4,068,599. These prior art methods relate particularly to features to assure completely filling the small diameter portion of the die cavity without having to exert excessive pressure. U.S. Pat. No. 4,008,599, in particular, suggests the use of a punch whose outer diameter is approximately equal to the diameter of a circle defined by the intersection of the bottom of the die cavity with the pitch cone of the bevel gear grooves and ridges, at a tolerance not exceeding a 20-percent diameter difference. This patent discloses also a truncated cone projecting from the punch and matching a cone defined by the ridges of the bevel gear cavity. Since the diameter of the punch is a parameter for determining the diameter of the blank, it appears inevitable that the blank sits on the ridges. Consequently, the die will wear out at these parts. The methods as per these references are very satisfactory from a point of view of avoiding the making of incomplete gears; but the dies wear out rather rapidly.